The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
H.264/AVC is a video codec standard providing the highest compression rate among the video codec standards up to now. In order to improve compression efficiency, the H.264/AVC standard prediction-encodes an image by using intra prediction reflecting directivity, integer transform in unit of 4×4 pixels, block modes having various sizes of 16×16 pixels to 4×4 pixels, or a deblocking filter. In addition, in order to find a more accurate motion vector, the H.264/AVC standard performs motion estimation by interpolating an image in units of a ½ pixel to ¼ pixel.
However, as described above, since by the H.264/AVC standard, motions vectors of various resolutions are determined and encoded by estimating a motion at various resolutions such as a ½ pixel unit and a ¼ pixel unit, a long codeword is used to encode a motion vector with a resolution of ½ pixel unit or ¼ pixel unit. Therefore, the number of bits required to encode a small motion vector increases, and the number of bits of a bitstream encoded increases, thus degrading compression efficiency.
In addition, since motion vector decoding is performed adaptively to motion vector encoding, when the compression efficiency of motion vector encoding is degraded, it is difficult to expect high efficiency in motion vector decoding.